The warm-up time, the time it takes for the temperature of the nuclear spins to rise from \(T_{n,1}\)  to \(T_{n,2}\) , is expected[1]} to be
\(t=\left( \frac{\lambda _n B_\mathrm {f}^2}{\mu _0 \dot{Q}}\right)\left(\frac{1}{T_{n,1}} - \frac{1}{T_{n,2}}\right)\) 
